Chemistry Commons^™

Solution And Solid-State Emission Toggling Of A Photochromic Hydrazone, Baihao Shao, Massimo Baroncini, Laura Bussotti, Mariangela Di Donato, Alberto Credi, Ivan Aprahamian

Dartmouth Scholarship

The proliferation of light-activated switches in recent years has enabled their use in a broad range of applications encompassing an array of research fields and disciplines. All current systems, however, have limitations (e.g., from complicated synthesis to incompatibility in biologically relevant media and lack of switching in the solid-state) that can stifle their real-life application. Here we report on a system that packs most, if not all, the desired, targeted and sought-after traits from photochromic compounds (bistability, switching in various media ranging from serum to solid-state, while exhibiting ON/OFF fluorescence emission switching, and two-photon assisted near-infrared light toggling) in an …

Surprising Antibacterial Activity And Selectivity Of Hydrophilic Polyphosphoniums Featuring Sugar And Hydroxy Substituents., Tyler J Cuthbert, Benjamin Hisey, Tristan D Harrison, John F Trant, Elizabeth R Gillies, Paul J Ragogna

Chemistry Publications

There is currently an urgent need for the development of new antibacterial agents to combat the spread of antibiotic-resistant bacteria. We explored the synthesis and antibacterial activities of novel, sugar-functionalized phosphonium polymers. While these compounds exhibited antibacterial activity, we unexpectedly found that the control polymer poly(tris(hydroxypropyl)vinylbenzylphosphonium chloride) showed very high activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and very low haemolytic activity against red blood cells. These results challenge the conventional wisdom in the field that lipophilic alkyl substituents are required for high antibacterial activity and opens prospects for new classes of antibacterial polymers.

Efforts Towards The Discovery Of Novel Methods For The Synthesis Of Pharmacologically Relevant Molecular Scaffolds, Graham Joseph Haun

Theses and Dissertations

With the introductions of pharmaceuticals into modern day society many people have been using them to improve their lives. Due to this high increase in demand along with the ever-growing concern of environmental impact pharmaceutical companies have been pressed to synthesis new and existing drugs at a higher rate. This increased rate can cause low yield drugs or have a heavy environmental impact. As the use of pharmaceuticals becomes more widespread the need for greener and simpler organic synthesis methods to make these pharmaceuticals becomes more needed.

Herein is reported the methodological development of different pharmacologically relevant scaffolds. This work …

A Synthetic Model Of The Nonheme Iron–Superoxo Intermediate Of Cysteine Dioxygenase, Anne A. Fischer, Sergey V. Lindeman, Adam T. Fiedler

Chemistry Faculty Research and Publications

A nonheme Fe(II) complex (1) that models substrate-bound cysteine dioxygenase (CDO) reacts with O₂ at −80 °C to yield a purple intermediate (2). Analysis with spectroscopic and computational methods determined that 2 features a thiolate-ligated Fe(III) center bound to a superoxide radical, mimicking the putative structure of a key CDO intermediate.

An Updated Description Of The Hydrogen Bond And Related Noncovalent Bonds, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The hydrogen bond is typically introduced briefly in General Chemistry as a simple electrostatic phenomenon involving a small and select group of atoms, a definition which is typically unchanged through higher levels in the curriculum. But this definition has undergone dramatic modernization of which students should be made aware. The original formulation in terms of only F, O, and N atoms has broadened very considerably, encompassing C as well as atoms from lower rows in the periodic table. The influence of hybridization, substituents, and overall charge cannot be overlooked. In addition to the Coulombic attraction, there are other “covalent” contributors …

The Role Of Proton Transport In Gating Current In A Voltage Gated Ion Channel, As Shown By Quantum Calculations, Alisher M. Kariev, Michael E. Green

Publications and Research

Over two-thirds of a century ago, Hodgkin and Huxley proposed the existence of voltage gated ion channels (VGIC) to carry Na⁺ and K⁺ ions across the cell membrane to create the nerve impulse, in response to depolarization of the membrane. The channels have multiple physiological roles, and play a central role in a wide variety of diseases when they malfunction. The first channel structure was found by MacKinnon and coworkers in 1998. Subsequently the structure of a number of VGIC was determined in the open (ion conducting) state. This type of channel consists of four voltage sensing domains …

Triel-Bonded Complexes Between Trr3 (Tr = B, Al, Ga; R = H, F, Cl, Br, Ch3) And Pyrazine, Mariusz Michalczyk, Wiktor Zierkiewicz, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Complexes between TrR3 (Tr = B, Al, Ga; R= H, F, Cl, Br, CH3)molecules and pyrazine have been characterized at the MP2 and CCSD(T) levels of theory. The adducts can be grouped according to the type of molecular arrangement. The first situation places the Tr atom in the plane of the pyrazine ring and contains a triel bond to the N lone pair. For the boron complexes the orbital interaction energy is almost equal to the electrostatic component, while the former is only half the latter for Tr= Al and Ga. The two monomers are stacked above one another in …

Molecular Insights On Aging And Aqueous-Phase Processing From Ambient Biomass Burning Emissions-Influenced Po Valley Fog And Aerosol, Matthew Brege, Marco Paglione, Stefania Gilardoni, Maria Cristina Facchini, Lynn Mazzoleni

Department of Chemistry Publications

To study the influence of regional biomass burning emissions and secondary processes, ambient samples of fog and aerosol were collected in the Po Valley (Italy) during the 2013 Supersito field campaign. After the extent of fresh vs. aged biomass burning influence was estimated from proton nuclear magnetic resonance (¹H NMR) and high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), two samples of fog water and two samples of PM1 aerosol were selected for ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Molecular compositions indicated that the water-soluble organic matter was largely non-polymeric without clearly repeating units. The …

Dft-Assisted Design And Evaluation Of Bifunctional Copper(I) Catalysts For The Direct Intermolecular Addition Of Aldehydes And Ketones To Alkynes, Jacob D. Porter, Eric Greve, Abdulmohsen Alsafran, Adam R. Benoit, Sergey V. Lindeman, Chris Dockendorff

Chemistry Faculty Research and Publications

Bifunctional catalysts containing discrete metal pi-acid and amine sites were designed and investigated for the direct intermolecular addition of aldehydes and ketones to unactivated alkynes. Copper(I)-based catalysts were prioritized based on intramolecular (Conia-ene type) reactions, and complexes were designed with tridentate ligands and potentially hemilabile heterocyclic spacers. The structures of the designed catalysts were computed using density functional theory (DFT), and the relative energies of putative catalytic intermediates were estimated and used to prioritize catalyst designs. Novel bifunctional precatalysts containing a thiazole spacer were synthesized via a 9-step sequence and combined with transition metals before screening for the direct addition …

How To Fold And Protect Mitochondrial Ribosomal Rna With Fewer Guanines, Maryam Hosseini, Poorna Roy, Marie Sissler, Craig L. Zirbel, Eric Westhof, Neocles B. Leontis

Chemistry Faculty Publications

Mammalian mitochondrial ribosomes evolved from bacterial ribosomes by reduction of ribosomal RNAs, increase of ribosomal protein content, and loss of guanine nucleotides. Guanine is the base most sensitive to oxidative damage. By systematically comparing high-quality, small ribosomal subunit RNA sequence alignments and solved 3D ribosome structures from mammalian mitochondria and bacteria, we deduce rules for folding a complex RNA with the remaining guanines shielded from solvent. Almost all conserved guanines in both bacterial and mammalian mitochondrial ribosomal RNA form guaninespecific, local or long-range, RNA–RNA or RNA– protein interactions. Many solvent-exposed guanines conserved in bacteria are replaced in mammalian mitochondria by …

Isolation Of Rna From A Mixture And Its Detection By Utilizing A Microgel-Based Optical Device, Molla R. Islam, Shakiba Azimi, Faranak Teimoory, Glen Loppnow, Michael J. Serpe

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

In this investigation, we show that RNA can be separated from a solution containing DNA and RNA and the isolated RNA can be detected using poly (N-isopropylacrylamide-co-N-(3-aminopropyl) methacrylamide hydrochloride) microgel-based optical devices (etalons). The isolation of RNA was accomplished by using hairpin-functionalized magnetic beads (MMPDNA) and differential melting, based on the fact that the DNA–RNA hybrid duplex is stronger (i.e., high melting temperature) than the DNA–DNA duplex (i.e., low melting temperature). By performing concurrent etalon sensing and fluorescent studies, we found that the MMPDNA combined with differential melting was capable of selectively separating RNA from DNA. This selective separation and …

Unraveling The Stereodynamics Of Cold Controlled Hd−H2 Collisions, James F. E. Croft, Naduvalath Balakrishnan, Meng Huang, Hua Guo

Chemistry and Biochemistry Faculty Research

Measuring inelastic rates with partial-wave resolution requires temperatures close to a Kelvin or below, even for the lightest molecule. In a recent experiment, Perreault, Mukherjee, and Zare [Nat. Chem. 10, 561 (2018).] studied collisional relaxation of excited HD molecules in the v=1, j=2 state by para- and ortho-H2 at a temperature of about 1 K, extracting the angular distribution of scattered HD in the v=1, j=0 state. By state preparation of the HD molecules, control of the angular distribution of scattered HD was demonstrated. Here, we report a first-principles simulation of that experiment which enables us to attribute the main …

Ability Of Ir And Nmr Spectral Data To Distinguish Between A Tetrel Bond And A Hydrogen Bond, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The placement of a nucleophile X along the R-CH3 axis of a methyl group can be described as either a trifurcated H-bond or as a tetrel bond between C and X. Quantum calculation of the vibrational and NMR spectral features of a number of systems are used to provide a framework by which to distinguish between the presence of a tetrel or H-bond. Both cationic and neutral methyl-containing Lewis acids (SMe3+, NMe4+, SMe2) are paired with both neutral and anionic Lewis bases (NH3, OH2, OCHNH2, OCH3-, OH-, HCOO-). As the base is moved away from the R-CH3 axis of the …

Composition Sorbents For Sewage Treatment Based On Karakalpakstan Bentonites, A Abdikamalova

Karakalpak Scientific Journal

The article presents the results of the investigation of the adsorption ability of bentonite clays of Karakalpakstan in relation to ions of heavy metals and petroleum products. It has been established that thermal activation in the presence of plant material waste leads to a change in the surface properties of bentonites, thereby increasing their adsorption properties with respect to various pollutants of waste water.

Short-Term Low Salinity Mitigates Effects Of Oil And Dispersant On Juvenile Eastern Oysters: A Laboratory Experiment With Implications For Oil Spill Response Activities, Meagan N. Schrandt, Sean Powers, F.Scott Rikard, Wilawan Thongda, Eric Peatman

University Faculty and Staff Publications

Following the Deepwater Horizon oil spill, eastern oyster (Crassostrea virginica) reefs in the northern Gulf of Mexico were exposed to oil and various associated clean-up activities that may have compromised oyster reef health. Included in the exposure was oil, dispersant, and in some locales, atypical salinity regimes. Oil and dispersants can be detrimental to oysters and the effects of salinity depend on the level. In addition to these extrinsic factors, genetic diversity of oyster populations may help the oysters respond to stressors, as demonstrated in other systems. We used a 3×3×2 factorial design to experimentally examine the effects …

An Overview Of Dynamic Heterogeneous Oxidations In The Troposphere, Elizabeth A. Pillar-Little, Marcelo I. Guzman

Chemistry Faculty Publications

Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. …

Deep Soils Modify Environmental Consequences Of Increased Nitrogen Fertilizer Use In Intensifying Amazon Agriculture, Kathijo Jankowski, Christopher Neill, Eric A. Davidson, Marcia Macedo, Ciniro Costa Jr., Gillian L. Galford, Leonardo Maracahipes Santos, Paul Lefebvre, Darlisson Nunes, Carlos E. P. Cerri, Richard Mchorney, Christine S. O'Connell, Michael T. Coe

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Agricultural intensification offers potential to grow more food while reducing the conversion of native ecosystems to croplands. However, intensification also risks environmental degradation through emissions of the greenhouse gas nitrous oxide (N₂O) and nitrate leaching to ground and surface waters. Intensively-managed croplands and nitrogen (N) fertilizer use are expanding rapidly in tropical regions. We quantified fertilizer responses of maize yield, N₂O emissions, and N leaching in an Amazon soybean-maize double-cropping system on deep, highly-weathered soils in Mato Grosso, Brazil. Application of N fertilizer above 80 kg N ha⁻¹ yr⁻¹ increased maize yield and N …

Enhancement Of Triplet-Sensitized Upconversion In Rigid Polymers Via Singlet Exciton Sink Approach, Steponas Raišys, Saulius Juršėnas, Yoan C. Simon, Christoph Weder, Karolis Kazlauskas

Faculty Publications

To increase the practical usefulness of solid-state sensitized upconversion (UC) materials as components of solar energy harvesting systems, it is important to identify and suppress loss mechanisms, and increase the UC quantum yield (Φ_UC). Here we focus on a benchmark UC system consisting of the emitter 9,10-diphenylanthracene (DPA) and the sensitizer platinum octaethylporphyrin (PtOEP) in a rigid poly(methyl methacrylate) (PMMA) matrix, and show that one of the major losses originates from Förster resonant energy transfer (FRET) from DPA back to PtOEP. Even though DPA emission lies within the PtOEP transparency window, the quantitative assessment of singlet exciton diffusion …

Gold-Catalyzed Conversion Of Lignin To Low Molecular Weight Aromatics, Yang Song, Justin K. Mobley, Ali Hussain Motagamwala, Mark Isaacs, James E. Dumesic, John Ralph, Adam F. Lee, Karen Wilson, Mark Crocker

Chemistry Faculty Publications

A heterogeneous catalyst system, employing Au nanoparticles (NPs) and Li–Al (1 : 2) layered double hydroxide (LDH) as support, showed excellent activity in aerobic oxidation of the benzylic alcohol group in β-O-4 linked lignin model dimers to the corresponding carbonyl products using molecular oxygen under atmospheric pressure. The synergistic effect between Au NPs and the basic Li–Al LDH support induces further reaction of the oxidized model compounds, facilitating facile cleavage of the β-O-4 linkage. Extension to oxidation of γ-valerolactone (GVL) extracted lignin and kraft lignin using Au/Li–Al LDH under similar conditions produced a range of aromatic monomers in high yield. …

Preparation And Characterization Of Chemically-Modified Biomaterials And Their Application As Adsorbents Of Penicillin G, Jesie Silva, Lizebel Morante, Tesfamichael Demeke, Jacqueline Baah-Twum, Abel E. Navarro

Publications and Research

The prevalence of antibiotics in water creates microbial resistance and has a negative impact on the ecosystem. Biomaterials such as spent tea leaves are rich in functional groups and are suitable for chemical modification for diverse applications. This research proposes the use of spent tea leaves of chamomile (CM), green tea (GT), and peppermint (PM) as structural scaffolds for the incorporation of carboxyl, sulfonyl, and thiol groups to improve the adsorption of Penicillin G (Pe). Adsorbents characterization reported a higher number of acidic functional groups, mainly in thiolated products. Scanning electron microscopy (SEM) analysis showed changes on the surfaces of …

Synthesis Of A Novel Bicyclic Scaffold Inspired By The Antifungal Natural Product Sordarin, Yibiao Wu, Chris Dockendorff

Chemistry Faculty Research and Publications

A simplified bicyclic scaffold inspired by the antifungal natural product sordarin was designed and synthesized which maintains the carboxylic acid/aldehyde (or nitrile) pharmacophore. Docking studies with the target for sordarin, the fungal protein eukaryotic elongation factor 2 (eEF2), suggested that the novel scaffolds may bind productively. A densely functionalized chiral cyclopentadiene was constructed in 8 steps and utilized in a Diels-Alder reaction with acrylonitrile. The resulting [2.2.1] cycloheptene was transformed into a scaffold possessing vicinal carboxylic acid and nitrile groups, with orientations predicted to provide high affinity for eEF2. The synthetic approach disclosed here sets the stage for a renewed …

Synthesis And Evaluation Of 4-Cycloheptylphenols As Selective Estrogen Receptor-Β Agonists (Serbas), K. L. Iresha Sampathi Perera, Alicia M. Hanson, Sergey V. Lindeman, Andrea Imhoff, Xingyun Lu, Daniel S. Sem, William A. Donaldson

Chemistry Faculty Research and Publications

A short and efficient route to 4-(4-hydroxyphenyl)cycloheptanemethanol was developed, which resulted in the preparation of a mixture of 4 stereoisomers. The stereoisomers were separated by preparative HPLC, and two of the stereoisomers identified by X-ray crystallography. The stereoisomers, as well as a small family of 4-cycloheptylphenol derivatives, were evaluated as estrogen receptor-beta agonists. The lead compound, 4-(4-hydroxyphenyl)cycloheptanemethanol was selective for activating ER relative to seven other nuclear hormone receptors, with 300-fold selectivity for the β over α isoform and with EC₅₀ of 30–50 nM in cell-based and direct binding assays.

Solid State Nmr Spectroscopy/Imaging In Situ Measuring Devices And Methods For Calibration And Determining One Or More Quantitative Properties Of A Target Sample, Lingyu Chi, Ming Huang, Rex E. Gerald, Klaus Woelk

Chemistry Faculty Research & Creative Works

In situ measuring devices, methods of making the same, and methods of using the same are provided herein. The in situ measuring devices can include a capillary tube having a reference material sealed inside the capillary tube, where the capillary tube is positioned inside of a solid state or MAS NMR rotor. A target sample can also be positioned in the interior of the solid state or MAS NMR rotor but is sequestered from the reference material by a capillary tube wall. The in situ measuring devices can be used in solid state MAS NMR spectroscopy to quantify one or …

Solid State Nmr Spectroscopy/Imaging In Situ Measuring Devices And Methods For Calibration And Determining One Or More Quantitative Properties Of A Target Sampleabstract, Lingyu Chi, Ming Huang, R. Gerald Ii, Klaus Woelk

Chemistry Faculty Research & Creative Works

In situ measuring devices, methods of making the same, and methods of using the same are provided herein. The in situ measuring devices can include a capillary tube having a reference material sealed inside the capillary tube, where the capillary tube is positioned inside of a solid state or MAS NMR rotor. A target sample can also be positioned in the interior of the solid state or MAS NMR rotor but is sequestered from the reference material by a capillary tube wall. The in situ measuring devices can be used in solid state MAS NMR spectroscopy to quantify one or …

Archean Phosphorus Liberation Induced By Iron Redox Geochemistry, Barry Herschy, Sae Jung Chang, Ruth Blake, Aivo Lepland, Heather Abbott-Lyon, Jacqueline Sampson, Zachary Atlas, Terence P. Kee, Matthew A. Pasek

Faculty Articles

The element phosphorus (P) is central to ecosystem growth and is proposed to be a limiting nutrient for life. The Archean ocean may have been strongly phosphorus-limited due to the selective binding of phosphate to iron oxyhydroxide. Here we report a new route to solubilizing phosphorus in the ancient oceans: reduction of phosphate to phosphite by iron(II) at low (<200 >°C) diagenetic temperatures. Reduction of phosphate to phosphite was likely widespread in the Archean, as the reaction occurs rapidly and is demonstrated from thermochemical modeling, experimental analogs, and detection of phosphite in early Archean rocks. We further demonstrate that the …

Crystal Structure Of [Mu-1kappa^2c^1,C^4:2(1,2,3,4-Eta)-1,2,3,4-Tetraphenylbuta-1,3-Diene-1,4-Diyl]Bis(Tricarbonylosmium)(Os---Os), Gregory Powell, Cynthia Powell

Chemistry and Biochemistry

In the title complex C34H20O6Os2 or (mu-eta^4-C4Ph4}$)Os2(CO)6, one Os atom is part of a metallacyclopentadiene ring, while the second Os atom is pi-bonded to the organic portion of this ring. The distance of 2.7494(2)A between the two Os atoms is typical of an Os---Os single bond. Three carbonyl ligands are attached to each Os atom and these six carbonyls adopt an eclipsed conformation. There are no bridging or semibridging CO groups. Two carbonyl ligands and all four phenyl groups are disordered over two slightly different positions for which each atom in the minor components is displaced less than 1A from …

Molecular Recognition Of Methionine-Terminated Peptides By Cucurbit[8]Uril, Zoheb Hirani, Hailey F. Taylor, E. F. Babcock, Andrew T. Bockus, C. D. Varnado Jr., Christopher W. Bielawski, Adam R. Urbach

Chemistry Faculty Research

This Article describes the molecular recognition of peptides containing an N-terminal methionine (Met) by the synthetic receptor cucurbit[8]-uril (Q8) in aqueous solution and with submicromolar affinity. Prior work established that Q8 binds with high affinity to peptides containing aromatic amino acids, either by simultaneous binding of two aromatic residues, one from each of two different peptides, or by simultaneous binding of an aromatic residue and its immediate neighbor on the same peptide. The additional binding interface of two neighboring residues suggested the possibility of targeting nonaromatic peptides, which have thus far bound only weakly to synthetic receptors. A peptide library …

Atomically Dispersed Pd On Nanodiamond/Graphene Hybrid For Selective Hydrogenation Of Acetylene, Fei Huang, Yuchen Deng, Yunlei Chen, Xiangbin Cai, Mia Peng, Zhimin Jia, Pengju Ren, Dequan Xiao, Xiaodong Wen, Ning Wang, Hongyang Liu, Ding Ma

Chemistry and Chemical Engineering Faculty Publications

An atomically dispersed palladium (Pd) catalyst supported onto a defective nanodiamond-graphene (ND@G) is reported here for selective hydrogenation of acetylene in the presence of abundant ethylene. The catalyst exhibits remarkable performance for the selective conversion of acetylene to ethylene: high conversion (100%), ethylene selectivity (90%), and good stability (i.e., steady for at least 30 hours). The unique struc-ture of the catalyst (i.e., atomically dispersion of Pd atoms on graphene through Pd-C bond anchoring) ensure the facile desorption of ethylene against the over-hydrogenation of ethylene to undesired ethane, which is the key for the outstanding selectivity of the catalyst.

Assembling Of Niox/Mwcnts-Gc Anodic Nanocatalyst For Water Electrolysis Applications, Yaser M. Asal Mr., Islam M. Al-Akraa Dr, Saher D. Khamis Eng

Chemical Engineering

Glassy carbon (GC) electrode is intended to be modified with nickel oxide (NiOx) and multiwalled carbon nanotubes (MWCNTs) in the anodic reaction of water electrolysis. NiOx deposition time is optimized and a 5 min was enough to attain the maximum activity. A further modification of the catalyst with MWCNTs could greatly enhance its stability during continuous electrolysis. As an outcome, an energy amount of 21.7 kWh/KgO₂ is minimized. Several electrochemical and materials characterization setups will be utilized to test the catalyst activity and to know its geometry and structure.

Native V. Californicum Alkaloid Combinations Induce Differential Inhibition Of Sonic Hedgehog Signaling, Matthew W. Turner, Roberto Cruz, Jordan Elwell, John French, Jared Mattos, Owen M. Mcdougal

Chemistry and Biochemistry Faculty Publications and Presentations

Veratrum californicum is a rich source of steroidal alkaloids such as cyclopamine, a known inhibitor of the Hedgehog (Hh) signaling pathway. Here we provide a detailed analysis of the alkaloid composition of V. californicum by plant part through quantitative analysis of cyclopamine, veratramine, muldamine and isorubijervine in the leaf, stem and root/rhizome of the plant. To determine whether additional alkaloids in the extracts contribute to Hh signaling inhibition, the concentrations of these four alkaloids present in extracts were replicated using commercially available standards, followed by comparison of extracts to alkaloid standard mixtures for inhibition of Hh signaling using Shh-Light II …